Optical Switching for Tuning Direction of LIDAR Output Signals

ABSTRACT

An optical system has a LIDAR chip that includes a switch configured to direct an outgoing LIDAR signal to one of multiple different alternate waveguides. The system also includes a redirection component configured to receive the outgoing LIDAR signal from any one of the alternate waveguides. The redirection component is also configured to redirect the received outgoing LIDAR signal such that a direction that the outgoing LIDAR signal travels away from the redirection component changes in response to changes in the alternate waveguide to which the optical switch directs the outgoing LIDAR signal.

RELATED APPLICATIONS

This Patent Application is a Divisional of U.S. patent application Ser.No. 16/277,790, filed on Feb. 15, 2019, entitled “Optical Switching forTuning Direction of LIDAR Output Signals” and incorporated herein in itsentirety; and U.S. patent application Ser. No. 16/277,790 claims thebenefit of U.S. Provisional Patent Application Ser. No. 62/689,716,filed on Jun. 25, 2018, entitled “Optical Sensor System” andincorporated herein in its entirety.

FIELD

The invention relates to optical devices. In particular, the inventionrelates to LIDAR chips.

BACKGROUND

There is an increasing commercial demand for 3D sensing systems that canbe economically deployed in applications such as ADAS (Advanced DriverAssistance Systems) and AR (Augmented Reality). LIDAR (Light Detectionand Ranging) sensors are used to construct a 3D image of a target sceneby illuminating the scene with laser light and measuring the returnedsignal.

Frequency Modulated Continuous Wave (FMCW) is an example of a coherentdetection method can be used for LIDAR applications. The FMCW techniqueis capable of determining both distance and velocity of an object with asingle measurement. Additionally, FMCW techniques have reducedsensitivity to ambient light and light from other LIDAR systems.

For many LIDAR applications there is a need to scan the light beamexternally to build up an image of the field of view. Methods ofscanning the beam include mechanical methods such as rotating theassembly containing the lasers, rotating mechanical mirrors, and MEMSmirrors. ‘Solid-state’ approaches are of interest due to their lack ofmoving parts and may improve scanning speeds. However, the solid-stateapproaches that have been tried have limited angular ranges and requirea large number of control elements. As a result, there is a need for apractical solid-state scanning mechanism.

SUMMARY

An optical system has a LIDAR chip that includes a switch configured todirect an outgoing LIDAR signal to one of multiple different alternatewaveguides. The system also includes a redirection component configuredto receive the outgoing LIDAR signal from any one of the alternatewaveguides. The redirection component is also configured to redirect thereceived outgoing LIDAR signal such that a direction that the outgoingLIDAR signal travels away from the redirection component is a functionof the alternate waveguide from which the redirection component receivesthe outgoing LIDAR signal.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a top view of a LIDAR chip.

FIG. 2 is a cross-section of a LIDAR chip according to FIG. 1constructed from a silicon-on-insulator wafer.

FIG. 3 illustrates the LIDAR chip of FIG. 1 used with an off-chipscanning mechanism.

FIG. 4 illustrates the LIDAR chip of FIG. 1 used with another embodimentof an off-chip scanning mechanism.

FIG. 5 is a cross section of the LIDAR chip of FIG. 1 having anintegrated scanning mechanism.

FIG. 6 is a schematic of a LIDAR system that includes a LIDAR chip and aredirection component.

FIG. 7 illustrates the focal points for a lens located along an arcedline.

FIG. 8A illustrates a LIDAR the chip having alternate waveguides thatterminate at facets positioned along an arced line.

FIG. 8B illustrates a LIDAR the chip having alternate waveguides thatterminate at facets. At least a portion of the alternate waveguides arecurved so that outgoing LIDAR signals approach the facets from differentdirections.

FIG. 9 illustrates a LIDAR chip having alternate waveguides thatterminate at facets positioned along a line angled such that the facetsfor alternate waveguides n=f through n=N are positioned along anapproximation of an arced focal point line.

FIG. 10 illustrates a LIDAR chip having alternate waveguides thatterminate at facets positioned such that a straight line can passthrough each of the facets. The LIDAR chip is positioned such that aportion of the facets are positioned on one side of an arced focal pointline and another portion of the facets are positioned on another side ofthe arced focal point line and the arced focal point line passes throughthe straight line through the facets at least twice.

FIG. 11 is a topview of a LIDAR chip having a lens integrated into theLIDAR chip.

FIG. 12A is a topview of a schematic of a LIDAR system that includes aLIDAR chip and another embodiment of a redirection component. Theredirection component outputs multiple different modes of a LIDAR outputsignal.

FIG. 12B is the schematic of FIG. 12A modified to show overlappingangular ranges for a portion of the LIDAR output signal modes shown inFIG. 12A.

DESCRIPTION

A LIDAR system has a LIDAR chip that includes a switch configured todirect an outgoing LIDAR signal to any one of multiple differentalternate waveguides. A redirection component receives the outgoingLIDAR signal from any one of the alternate waveguides. The redirectioncomponent also redirects the received outgoing LIDAR signal such that adirection that the outgoing LIDAR signal travels away from theredirection component changes in response to changes in the alternatewaveguide from which the redirection component receives the outgoingLIDAR signal. As a result, the outgoing LIDAR signal can be steered todifferent sample regions in a field of view by operating the opticalswitch so as to change the alternate waveguides to which the outgoingLIDAR signal is directed. The optical switch can be a solid-stateoptical switch that includes or consists of optical components such ascascaded 2×2 Mach-Zehnder (MZ) modulators interferometers. Additionally,an example of a suitable redirection component is one or more lensesand/or one or more mirrors. The one or more lenses and/or one or moremirrors can be stationary relative to the optical switch. As a result,steering of the outgoing LIDAR signal can be achieved with a practicalsolid-state device. Additionally, the angular range over which theoutgoing LIDAR signal can be steered can be increased by increasing theseparation between the alternate waveguides. As a result, the LIDARsystem can have a solid-state steering mechanism with a wide angularrange.

Another example of a suitable redirection component includes a splitterconfigured to receive the outgoing LIDAR signal from any one of thealternate waveguides and to split the outgoing LIDAR signal into outputsignals. The redirection component also includes multiple steeringwaveguides that are each configured to receive a different one of theoutput signals. The steering waveguides each terminates at a facet andthe facets are arranged such that output signals exiting from thesteering waveguides through the facets re-form the outgoing LIDAR signalwith the re-formed outgoing LIDAR signal traveling away from theredirection component. At least a portion of the steering waveguideseach includes a phase tuner configured to tune a phase differentialbetween the output signals such the direction that the reformed outgoingLIDAR signal travels away from the redirection component changes. As aresult, steering of the LIDAR output signal can be achieved with boththe phase tuners and selection of the alternate waveguide. Thiscombination of steering mechanisms allows the outgoing LIDAR signal tobe steered continuously within a field of view. Additionally, thesplitter, steering waveguides and phase tuners can all exclude movingparts. As a result, the steering of the outgoing LIDAR signal can beachieved with a practical solid-state device. Further, the angular rangeover which the outgoing LIDAR signal can be steered can be increased byincreasing the separation between the alternate waveguides. As a result,the LIDAR system can have a solid-state steering mechanism with a wideangular range.

FIG. 1 is a topview of a LIDAR chip that includes a component assembly 8with a laser cavity. The laser cavity includes a light source 10 thatcan include or consist of a gain medium (not shown) for a laser. Thechip also includes a cavity waveguide 12 that receives a light signalfrom the light source 10. The light source can be positioned in a recess13 so a facet of the light source is optically aligned with a facet ofthe cavity waveguide 12 to allow the light source and cavity waveguide12 to exchange light signals. The cavity waveguide 12 carries the lightsignal to a partial return device 14. The illustrated partial returndevice 14 is an optical grating such as a Bragg grating. However, otherpartial return devices 14 can be used; for instance, mirrors can be usedin conjunction with echelle gratings and arrayed waveguide gratings.

The partial return device 14 returns a return portion of the lightsignal to the cavity waveguide 12 as a return signal. For instance, thecavity waveguide 12 returns the return signal to the light source 10such that the return portion of the light signal travels through thegain medium. The light source 10 is configured such that at least aportion of the return signal is added to the light signal that isreceived at the cavity waveguide 12. For instance, the light source 10can include a highly, fully, or partially reflective device 15 thatreflects the return signal received from the gain medium back into thegain medium. As a result, light can resonate between the partial returndevice 14 and the reflective device 15 so as to form a Distributed BraggReflector (DBR) laser cavity. A DBR laser cavity has an inherentlynarrow-linewidth and a longer coherence length than DFB lasers andaccordingly improves performance when an object reflecting the LIDARoutput signal from the chip is located further away from the chip.

The partial return device 14 passes a portion of the light signalreceived from the cavity waveguide 12 to a utility waveguide 16 includedon the chip. The portion of the light signal that the utility waveguide16 receives from the partial return device 14 serves as the output ofthe laser cavity. The output of the laser cavity serves as an outgoingLIDAR signal on the utility waveguide 16. The utility waveguide 16terminates at a facet 18 and carries the outgoing LIDAR signal to thefacet 18. The facet 18 can be positioned such that the outgoing LIDARsignal traveling through the facet 18 exits the chip and serves as aLIDAR output signal. For instance, the facet 18 can be positioned at anedge of the chip so the outgoing LIDAR signal traveling through thefacet 18 exits the chip and serves as a LIDAR output signal.

The LIDAR output signal travels away from the chip and is reflected byobjects in the path of the LIDAR signal. The reflected signal travelsaway from the objects. At least a portion of the reflected signalreturns to the facet 18 of the utility waveguide 16. Accordingly, aportion of the reflected signal can enter the utility waveguide 16through the facet 18 and serve as a LIDAR input signal guided by theutility waveguide 16.

The utility waveguide 16 can include a tapered portion before the facet18. For instance, the utility waveguide 16 can include a taper 20 thatterminate at the facet 18. The taper 20 can relax the alignmenttolerances required for efficient coupling of the utility waveguide 16to the LIDAR input light and the outgoing LIDAR signal. Accordingly, thetaper 20 can increase the percentage of the LIDAR input signal that issuccessfully returned to the chip for processing. In some instances, thetaper 20 is constructed such that the facet 18 has an area that is morethan two, five, or ten times the area of a cross section of a straightportion of the utility waveguide 16. Although FIG. 1 shows the taper 20as a horizontal taper, the taper 20 can be a horizontal and/or verticaltaper. The horizontal and/or vertical taper can be linear and/or curved.In some instances, the taper 20 is an adiabatic taper.

The chip includes a data branch 24 where the optical signals that areprocessed for LIDAR data (radial velocity and/or distance between areflecting object and the source of the LIDAR output signal) aregenerated. The data branch includes an optical coupler 26 that moves aportion of the light signals from the utility waveguide 16 into the databranch. For instance, an optical coupler 26 couples a portion of theoutgoing LIDAR signal from the utility waveguide 16 onto a referencewaveguide 27 as a reference signal. The reference waveguide 27 carriesthe reference signal to a light-combining component 28.

The optical coupler 26 also couples a portion of the LIDAR input signalfrom the utility waveguide 16 onto a comparative waveguide 30 as acomparative signal. The comparative signal includes at least a portionof the light from the LIDAR input signal. The comparative signal canexclude light from the reference light signal. The comparative waveguide30 carries the comparative signal to the light-combining component 28.

The illustrated optical coupler 26 is a result of positioning theutility waveguide 16 sufficiently close to the reference waveguide 27and the comparative waveguide 30 that light from the utility waveguide16 is coupled into the reference waveguide 27 and the comparativewaveguide 30; however, other signal tapping components can be used tomove a portion of the of the light signals from the utility waveguide 16onto the reference waveguide 27 and the comparative waveguide 30.Examples of suitable signal tapping components include, but are notlimited to, y-junctions, multi-mode interference couplers (MMIs), andintegrated optical circulators.

The light-combining component 28 combines the comparative signal and thereference signal into a composite signal. The reference signal includeslight from the outgoing LIDAR signal. For instance, the reference signalcan serve as a sample of the outgoing LIDAR signal. The reference signalcan exclude light from the LIDAR output signal and the LIDAR inputsignal. In contrast, the comparative signal light includes light fromthe LIDAR input signal. For instance, the comparative signal can serveas a sample of the LIDAR input signal. Accordingly, the comparativesignal has been reflected by an object located off of the chip while theLIDAR output signal has not been reflected. When the chip and thereflecting object are moving relative to one another, the comparativesignal and the reference signal have different frequencies due to theDoppler effect. As a result, beating occurs between the comparativesignal and the reference signal.

The light-combining component 28 also splits the resulting compositesample signal onto a first detector waveguide 36 and a second detectorwaveguide 38. The first detector waveguide 36 carries a first portion ofthe composite sample signal to a first light sensor 40 that converts thefirst portion of the composite sample signal to a first electricalsignal. The second detector waveguide 38 carries a second portion of thecomposite sample signal to a second light sensor 42 that converts thesecond portion of the composite sample signal to a second electricalsignal. Examples of suitable light sensors include germanium photodiodes(PDs), and avalanche photodiodes (APDs).

The light combining component 28, the first light sensor 40 and thesecond light sensor 42 can be connected as a balanced photodetector thatoutputs an electrical data signal. For instance, the light combiningcomponent 28, the first light sensor 40 and the second light sensor 42can be connected such that the DC components of the signal photocurrentscancel, improving detection sensitivity. Suitable methods for connectingthe first light sensor 40 and the second light sensor 42 as balancedphotodetectors includes connecting the first light sensor 40 and thesecond light sensor 42 in series. In one example, the first light sensor40 and the second light sensor 42 are both avalanche photodiodesconnected in series. Balanced photodetection is desirable for detectionof small signal fluctuations.

An example of a suitable light-combining component 28 is a Multi-ModeInterference (MMI) device such as a 2×2 MMI device. Other suitablelight-combining components 28 include, but are not limited to, adiabaticsplitters, and directional coupler. In some instances, the functions ofthe illustrated light-combining component 28 are performed by more thanone optical component or a combination of optical components.

A single light sensor can replace the first light sensor 40 and thesecond light sensor 42 and can output the data signal. When a singlelight sensor replaces the first light sensor 40 and the second lightsensor 42, the light-combining component 28 need not includelight-splitting functionality. As a result, the illustrated lightlight-combining component 28 can be a 2×1 light-combining componentrather than the illustrated 2×1 light-combining component. For instance,the illustrated light light-combining component can be a 2×1 MMI device.In these instances, the chip includes a single detector waveguide thatcarries the composite sample signal to the light sensor.

The data branch includes a data optical attenuator 44 positioned alongthe comparative waveguide 30 such that the data optical attenuator 44can be operated so as to attenuate the comparative signal on thecomparative waveguide 30. The chip also includes an output opticalattenuator 46 positioned along the utility waveguide 16 such that theoutput optical attenuator 46 can be operated so as to attenuate theoutgoing LIDAR signal on the utility waveguide 16. Suitable attenuatorsfor the data optical attenuator 44 and/or the output optical attenuator46 are configured to attenuate intensity of a light signal. Examples ofa suitable attenuator configured to attenuate intensity of a lightsignal include carrier injection based PIN diodes, electro-absorptionmodulators, and Mach-Zehnder (MZ) modulators.

The chip also includes a sampling directional coupler 50 that couples aportion of the comparative signal from the comparative waveguide 30 ontoa sampling waveguide 52. The coupled portion of the comparative signalserves as a sampling signal. The sampling waveguide 52 carries thesampling signal to a sampling light sensor 54. Although FIG. 1illustrates a sampling directional coupler 50 moving a portion of thecomparative signal onto the sampling waveguide 52, other signal tappingcomponents can be used to move a portion of the comparative signal fromthe comparative waveguide 30 onto the sampling waveguide 52. Examples ofsuitable signal tapping components include, but are not limited to,y-junctions, and MMIs.

The chip includes a control branch 55 for controlling operation of thelaser cavity. The control branch includes a directional coupler 56 thatmoves a portion of the outgoing LIDAR signal from the utility waveguide16 onto a control waveguide 57. The coupled portion of the outgoingLIDAR signal serves as a tapped signal. Although FIG. 1 illustrates adirectional coupler 56 moving portion of the outgoing LIDAR signal ontothe control waveguide 57, other signal-tapping components can be used tomove a portion of the outgoing LIDAR signal from the utility waveguide16 onto the control waveguide 57. Examples of suitable signal tappingcomponents include, but are not limited to, y-junctions, and MMIs.

The control waveguide 57 carries the tapped signal to an interferometer58 that splits the tapped signal and then re-combines the differentportions of the tapped signal with a phase differential between theportions of the tapped signal. The illustrated interferometer 58 is aMach-Zehnder interferometer; however, other interferometers can be used.

The interferometer 58 outputs a control light signal on aninterferometer waveguide 60. The interferometer waveguide 60 carries thecontrol light signal to a control light sensor 61 that converts thecontrol light signal to an electrical signal that serves as anelectrical control signal. The interferometer signal has an intensitythat is a function of the frequency of the outgoing LIDAR signal. Forinstance, a Mach-Zehnder interferometer will output a sinusoidal controllight signal with a fringe pattern. Changes to the frequency of theoutgoing LIDAR signal will cause changes to the frequency of the controllight signal. Accordingly, the frequency of the electrical controlsignal output from the control light sensor 61 is a function of thefrequency of the outgoing LIDAR signal. Other detection mechanisms canbe used in place of the control light sensor 61. For instance, thecontrol light sensor 61 can be replaced with a balanced photodetectorarranged as the light combining component 28, the first light sensor 40and the second light sensor 42.

Electronics 62 can operate one or more components on the chip. Forinstance, the electronics 62 can be in electrical communication with andcontrol operation of the light source 10, the data optical attenuator44, output optical attenuator 46, the first light sensor 40, the secondlight sensor 42, the sampling light sensor 54, and the control lightsensor 61. Although the electronics 62 are shown off the chip, all or aportion of the electronics can be included on the chip. For instance,the chip can include electrical conductors that connect the first lightsensor 40 in series with the second light sensor 42.

During operation of the chip, the electronics 62 operate the lightsource 10 such that the laser cavity outputs the outgoing LIDAR signal.The electronics 62 then operate the chip through a series of cycleswhere each cycle generates LIDAR data (radial velocity and/or distancebetween a reflecting object and the source of the LIDAR output signal)associated with one of the sample regions in the field of view. Eachcycle can include multiple sample periods. During each sample period,the electronics can tune the frequency of the outgoing LIDAR signal. Aswill be described in more detail below, the electronics can employoutput from the control branch in order to control the frequency of theoutgoing LIDAR signal such that the frequency of the outgoing LIDARsignal as a function of time is known to the electronics. In someinstance, a cycle includes a first sample period and a second sampleperiod. During the first sample period, the electronics 62 can increasethe frequency of the outgoing LIDAR signal and during the second sampleperiod the electronics 62 can decrease the frequency of the outgoingLIDAR signal. For instance, the laser cavity can be configured to outputan outgoing LIDAR signal (and accordingly a LIDAR output signal) with awavelength of 1550 nm. During the first sample period, the electronics62 can increase the frequency of the outgoing LIDAR signal (andaccordingly a LIDAR output signal) such that the wavelength decreasesfrom 1550 nm to 1459.98 nm followed by decreasing the frequency of theoutgoing LIDAR signal such that the wavelength increases from 1459.98 nmto 1550 nm.

When the outgoing LIDAR signal frequency is increased during the firstsample period, the LIDAR output signal travels away from the chip andthen returns to the chip as a LIDAR input signal. A portion of the LIDARinput signal becomes the comparative signal. During the time that theLIDAR output signal and the LIDAR input signal are traveling between thechip and a reflecting object, the frequency of the outgoing LIDAR signalcontinues to increase. Since a portion of the outgoing LIDAR signalbecomes the reference signal, the frequency of the reference signalcontinues to increase. As a result, the comparative signal enters thelight-combining component with a lower frequency than the referencesignal concurrently entering the light-combining component.Additionally, the further the reflecting object is located from thechip, the more the frequency of the reference signal increases beforethe LIDAR input signal returns to the chip. Accordingly, the larger thedifference between the frequency of the comparative signal and thefrequency of the reference signal, the further the reflecting object isfrom the chip. As a result, the difference between the frequency of thecomparative signal and the frequency of the reference signal is afunction of the distance between the chip and the reflecting object.

For the same reasons, when the outgoing LIDAR signal frequency isdecreased during the second sample period, the comparative signal entersthe light-combining component with a higher frequency than the referencesignal concurrently entering the light-combining component and thedifference between the frequency of the comparative signal and thefrequency of the reference signal during the second sample is alsofunction of the distance between the chip and the reflecting object.

In some instances, the difference between the frequency of thecomparative signal and the frequency of the reference signal can also bea function of the Doppler effect because relative movement of the chipand reflecting object can also affect the frequency of the comparativesignal. For instance, when the chip is moving toward or away from thereflecting object and/or the reflecting object is moving toward or awayfrom the chip, the Doppler effect can affect the frequency of thecomparative signal. Since the frequency of the comparative signal is afunction of the speed the reflecting object is moving toward or awayfrom the chip and/or the speed the chip is moving toward or away fromthe reflecting object, the difference between the frequency of thecomparative signal and the frequency of the reference signal is also afunction of the speed the reflecting object is moving toward or awayfrom the chip and/or the speed the chip is moving toward or away fromthe reflecting object. Accordingly, the difference between the frequencyof the comparative signal and the frequency of the reference signal is afunction of the distance between the chip and the reflecting object andis also a function of the Doppler effect.

The composite sample signal and the data signal each effectivelycompares the comparative signal and the reference signal. For instance,since the light-combining component combines the comparative signal andthe reference signal and these signals have different frequencies, thereis beating between the comparative signal and reference signal.Accordingly, the composite sample signal and the data signal have a beatfrequency related to the frequency difference between the comparativesignal and the reference signal and the beat frequency can be used todetermine the difference in the frequency of the comparative signal andthe reference signal. A higher beat frequency for the composite samplesignal and/or the data signal indicates a higher differential betweenthe frequencies of the comparative signal and the reference signal. As aresult, the beat frequency of the data signal is a function of thedistance between the chip and the reflecting object and is also afunction of the Doppler effect.

As noted above, the beat frequency is a function of two unknowns; thedistance between the chip and the reflecting object and the relativevelocity of the chip and the reflecting object (i.e., the contributionof the Doppler effect). The change in the frequency difference betweenthe comparative signal and the reference signal (Δf) is given byΔf=2Δvf/c where f is the frequency of the LIDAR output signal andaccordingly the reference signal, Δv is the relative velocity of thechip and the reflecting object and c is the speed of light in air. Theuse of multiple different sample periods permits the electronics 62 toresolve the two unknowns. For instance, the beat frequency determinedfrom the first sample period is related to the unknown distance andDoppler contribution and the beat frequency determined from the secondsample period is also related to the unknown distance and Dopplercontribution. The availability of the two relationships allows theelectronics 62 to resolve the two unknowns. Accordingly, the distancebetween the chip and the reflecting object can be determined withoutinfluence from the Doppler effect. Further, in some instances, theelectronics 62 use this distance in combination with the Doppler effectto determine the radial velocity of the reflecting object toward or awayfrom the LIDAR chip.

In instances where the radial velocity of target and source is zero orvery small, the contribution of the Doppler effect to the beat frequencyis essentially zero. In these instances, the Doppler effect does notmake a substantial contribution to the beat frequency and theelectronics 62 can use only the beat frequency from the first sampleperiod to determine the distance between the chip and the reflectingobject.

During operation, the electronics 62 can adjust the frequency of theoutgoing LIDAR signal in response to the electrical control signaloutput from the control light sensor 61. As noted above, the magnitudeof the electrical control signal output from the control light sensor 61is a function of the frequency of the outgoing LIDAR signal.Accordingly, the electronics 62 can adjust the frequency of the outgoingLIDAR signal in response to the magnitude of the control. For instance,while changing the frequency of the outgoing LIDAR signal during one ofthe sample periods, the electronics 62 can have a range of suitablevalues for the electrical control signal magnitude as a function oftime. At multiple different times during a sample period, theelectronics 62 can compare the electrical control signal magnitude tothe range of values associated with the current time in the sampleperiod. If the electrical control signal magnitude indicates that thefrequency of the outgoing LIDAR signal is outside the associated rangeof electrical control signal magnitudes, the electronics 62 can operatethe light source 10 so as to change the frequency of the outgoing LIDARsignal so it falls within the associated range. If the electricalcontrol signal magnitude indicates that the frequency of the outgoingLIDAR signal is within the associated range of electrical control signalmagnitudes, the electronics 62 do not change the frequency of theoutgoing LIDAR signal.

During operation, the electronics 62 can adjust the level of attenuationprovided by the output optical attenuator 46 in response to the samplingsignal from the sampling light sensor 54. For instance, the electronics62 operate the output optical attenuator 46 so as to increase the levelof attenuation in response to the magnitude of the sampling signal beingabove a first signal threshold and/or decrease the magnitude of thepower drop in response to the magnitude of the sampling signal beingbelow a second signal threshold.

In some instance, the electronics 62 adjust the level of attenuationprovided by the output optical attenuator 46 to prevent or reduce theeffects of back-reflection on the performance of the laser cavity. Forinstance, the first signal threshold and/or the second signal thresholdcan optionally be selected to prevent or reduce the effects ofback-reflection on the performance of the laser cavity. Back reflectionoccurs when a portion of the LIDAR input signal returns to the lasercavity as a returned LIDAR signal. In some instances, on the order of50% of the LIDAR input signal that passes through the facet 18 returnsto the laser cavity. The returned LIDAR signal can affect performance ofthe laser cavity when the power of the returned LIDAR signal enteringthe partial return device 14 does not decrease below the power of theoutgoing LIDAR signal exiting from the partial return device 14 (“powerdrop”) by more than a minimum power drop threshold. In the illustratedchip, the minimum power drop threshold can be around 35 dB (0.03%).Accordingly, the returned LIDAR signal can affect the performance of thelaser cavity when the power of the returned LIDAR signal entering thepartial return device 14 is not more than 35 dB below the power of theoutgoing LIDAR signal exiting from the partial return device 14.

The electronics 62 can operate the output optical attenuator 46 so as toreduce the effect of low power drops, e.g. when the target object isvery close or highly reflective or both. As is evident from FIG. 1,operation of the output optical attenuator 46 so as to increase thelevel of attenuation reduces the power of the returned LIDAR signalentering the partial return device 14 and also reduces the power of thereturned outgoing LIDAR signal at a location away from the partialreturn device 14. Since the output optical attenuator 46 is locatedapart from the partial return device 14, the power of the outgoing LIDARsignal exiting from the partial return device 14 is not directlyaffected by the operation of the output optical attenuator 46.Accordingly, the operation of the output optical attenuator 46 so as toincrease the level of attenuation increases the level of the power drop.As a result, the electronics can employ the optical attenuator 46 so asto tune the power drop.

Additionally, the magnitude of the sampling signal is related to thepower drop. For instance, the magnitude of the sampling signal isrelated to the power of the comparative signal as is evident fromFIG. 1. Since the comparative signal is a portion of the LIDAR inputsignal, the magnitude of the sampling signal is related to the power ofthe LIDAR input signal. This result means the magnitude of the samplingsignal is also related to the power of the returned LIDAR signal becausethe returned LIDAR signal is a portion of the LIDAR input signal.Accordingly, the magnitude of the sampling signal is related to thepower drop.

Since the magnitude of the sampling signal is related to the power drop,the electronics 62 can use the magnitude of the sampling signal tooperate the output optical attenuator so as to keep the magnitude of thecomparative signal power within a target range. For instance, theelectronics 62 can operate the output optical attenuator 46 so as toincrease the magnitude of the power drop in response to the samplingsignal indicating that the magnitude of power drop is at or below afirst threshold and/or the electronics 62 can operate the output opticalattenuator 46 so as to decrease the magnitude of the power drop inresponse to the sampling signal indicating that the magnitude of powerdrop is at or above a second threshold. In some instances, the firstthreshold is greater than or equal to the minimum power drop threshold.In one example, the electronics 62 operate the output optical attenuator46 so as to increase the magnitude of the power drop in response to themagnitude of the sampling signal being above a first signal thresholdand/or decrease the magnitude of the power drop in response to themagnitude of the sampling signal being below a second signal threshold.The identification of the value(s) for one, two, three, or fourvariables selected from the group consisting of the first threshold, thesecond threshold, the first signal threshold, and the second signalthreshold can be determined from calibration of the optical chip duringset-up of the LIDAR chip system.

Light sensors can become saturated when the power of the composite lightsignal exceeds a power threshold. When a light sensor becomes saturated,the magnitude of the data signal hits a maximum value that does notincrease despite additional increases in the power of the compositelight signal above the power threshold. Accordingly, data can be lostwhen the power of the composite light signal exceeds a power threshold.During operation, the electronics 62 can adjust the level of attenuationprovided by the data optical attenuator 44 so the power of the compositelight signal is maintained below a power threshold.

As is evident from FIG. 1, the magnitude of the sampling signal isrelated to the power of the comparative signal. Accordingly, theelectronics 62 can operate the data optical attenuator 44 in response tooutput from the sampling signal. For instance, the electronics 62 canoperate the data optical attenuator so as to increase attenuation of thecomparative signal when the magnitude of the sampling signal indicatesthe power of the comparative signal is above an upper comparative signalthreshold and/or can operate the data optical attenuator so as todecrease attenuation of the comparative signal when the magnitude of thesampling signal indicates the power of the comparative signal is below alower comparative signal threshold. For instance, in some instances, theelectronics 62 can increase attenuation of the comparative signal whenthe magnitude of the sampling signal is at or above an upper comparativethreshold and/or the electronics 62 decrease attenuation of thecomparative signal when the magnitude of the sampling signal is at orbelow an upper comparative signal threshold.

As noted above, the electronics 62 can adjust the level of attenuationprovided by the output optical attenuator 46 in response to the samplingsignal. The electronics 62 can adjust the level of attenuation providedby the data optical attenuator 44 in response to the sampling signal inaddition or as an alternative to adjusting the level of attenuationprovided by the output optical attenuator 46 in response to the samplingsignal

Suitable platforms for the chip include, but are not limited to, silica,indium phosphide, and silicon-on-insulator wafers. FIG. 2 is across-section of portion of a chip constructed from asilicon-on-insulator wafer. A silicon-on-insulator (SOI) wafer includesa buried layer 80 between a substrate 82 and a light-transmitting medium84. In a silicon-on-insulator wafer, the buried layer is silica whilethe substrate and the light-transmitting medium are silicon. Thesubstrate of an optical platform such as an SOI wafer can serve as thebase for the entire chip. For instance, the optical components shown inFIG. 1 can be positioned on or over the top and/or lateral sides of thesubstrate.

The portion of the chip illustrated in FIG. 2 includes a waveguideconstruction that is suitable for use with chips constructed fromsilicon-on-insulator wafers. A ridge 86 of the light-transmitting mediumextends away from slab regions 88 of the light-transmitting medium. Thelight signals are constrained between the top of the ridge and theburied oxide layer.

The dimensions of the ridge waveguide are labeled in FIG. 2. Forinstance, the ridge has a width labeled w and a height labeled h. Athickness of the slab regions is labeled T. For LIDAR applications,these dimensions are more important than other applications because ofthe need to use higher levels of optical power than are used in otherapplications. The ridge width (labeled w) is greater than 1 μm and lessthan 4 μm, the ridge height (labeled h) is greater than 1 μm and lessthan 4 μm, the slab region thickness is greater than 0.5 μm and lessthan 3 μm. These dimensions can apply to straight or substantiallystraight portions of the waveguide, curved portions of the waveguide andtapered portions of the waveguide(s). Accordingly, these portions of thewaveguide will be single mode. However, in some instances, thesedimensions apply to straight or substantially straight portions of awaveguide while curved portions of the waveguide and/or tapered portionsof the waveguide have dimensions outside of these ranges. For instance,the tapered portions of the utility waveguide 16 illustrated in FIG. 1can have a width and/or height that is >4 μm and can be in a range of 4μm to 12 μm. Additionally or alternately, curved portions of a waveguidecan have a reduced slab thickness in order to reduce optical loss in thecurved portions of the waveguide. For instance, a curved portion of awaveguide can have a ridge that extends away from a slab region with athickness greater than or equal to 0.0 μm and less than 0.5 μm. Whilethe above dimensions will generally provide the straight orsubstantially straight portions of a waveguide with a single-modeconstruction, they can result in the tapered section(s) and/or curvedsection(s) that are multimode. Coupling between the multi-mode geometryto the single mode geometry can be done using tapers that do notsubstantially excite the higher order modes. Accordingly, the waveguidescan be constructed such that the signals carried in the waveguides arecarried in a single mode even when carried in waveguide sections havingmulti-mode dimensions. The waveguide construction of FIG. 2 is suitablefor all or a portion of the waveguides selected from the groupconsisting of the cavity waveguide 12, utility waveguide 16, referencewaveguide 27, comparative waveguide 30, first detector waveguide 36,second detector waveguide 38, sampling waveguide 52, control waveguide57, and interferometer waveguide 60.

The light source 10 that is interfaced with the utility waveguide 16 canbe a gain element that is a component separate from the chip and thenattached to the chip. For instance, the light source 10 can be a gainelement that is attached to the chip using a flip-chip arrangement.

Use of flip-chip arrangements is suitable when the light source 10 is tobe interfaced with a ridge waveguide on a chip constructed fromsilicon-on-insulator wafer. Examples of suitable interfaces betweenflip-chip gain elements and ridge waveguides on chips constructed fromsilicon-on-insulator wafer can be found in U.S. Pat. No. 9,705,278,issued on Jul. 11, 2017 and in U.S. Pat. No. 5,991,484 issued on Nov. 231999; each of which is incorporated herein in its entirety. Theconstructions are suitable for use as the light source 10. When thelight source 10 is a gain element, the electronics 62 can change thefrequency of the outgoing LIDAR signal by changing the level ofelectrical current applied to through the gain element.

The attenuators can be a component that is separate from the chip andthen attached to the chip. For instance, the attenuator can be includedon an attenuator chip that is attached to the chip in a flip-chiparrangement. The use of attenuator chips is suitable for all or aportion of the attenuators selected from the group consisting of thedata attenuator and the control attenuator.

As an alternative to including an attenuator on a separate component,all or a portion of the attenuators can be integrated with the chip. Forinstance, examples of attenuators that are interfaced with ridgewaveguides on a chip constructed from a silicon-on-insulator wafer canbe found in U.S. Pat. No. 5,908,305, issued on Jun. 1 1999; each ofwhich is incorporated herein in its entirety. The use of attenuatorsthat are integrated with the chip are suitable for all or a portion ofthe light sensors selected from the group consisting of the dataattenuator and the control attenuator.

Light sensors that are interfaced with waveguides on a chip can be acomponent that is separate from the chip and then attached to the chip.For instance, the light sensor can be a photodiode, or an avalanchephotodiode. Examples of suitable light sensor components include, butare not limited to, InGaAs PIN photodiodes manufactured by Hamamatsulocated in Hamamatsu City, Japan, or an InGaAs APD (Avalanche PhotoDiode) manufactured by Hamamatsu located in Hamamatsu City, Japan. Theselight sensors can be centrally located on the chip as illustrated inFIG. 1. Alternately, all or a portion the waveguides that terminate at alight sensor can terminate at a facet 18 located at an edge of the chipand the light sensor can be attached to the edge of the chip over thefacet 18 such that the light sensor receives light that passes throughthe facet 18. The use of light sensors that are a separate componentfrom the chip is suitable for all or a portion of the light sensorsselected from the group consisting of the first light sensor 40, thesecond light sensor 42, the sampling light sensor 54, and the controllight sensor 61.

As an alternative to a light sensor that is a separate component, all ora portion of the light sensors can be integrated with the chip. Forinstance, examples of light sensors that are interfaced with ridgewaveguides on a chip constructed from a silicon-on-insulator wafer canbe found in Optics Express Vol. 15, No. 21, 13965-13971 (2007); U.S.Pat. No. 8,093,080, issued on Jan. 10 2012; U.S. Pat. No. 8,242,432,issued Aug. 14 2012; and U.S. Pat. No. 6,108,8472, issued on Aug. 22,2000 each of which is incorporated herein in its entirety. The use oflight sensors that are integrated with the chip are suitable for all ora portion of the light sensors selected from the group consisting of thefirst light sensor 40, the second light sensor 42, the sampling lightsensor 54, and the control light sensor 61.

Construction of optical gratings that are integrated with a variety ofoptical device platforms are available. For instance, a Bragg gratingcan be formed in a ridge waveguides by forming grooves in the top of theridge and/or in the later sides of the ridge.

In some instances, it is desirable to scan the LIDAR output signal. Theabove chip construction is suitable for use with various scanningmechanisms used in LIDAR applications. For instance, the output LIDARsignal can be received by one or more reflecting devices and/or one morecollimating devices. The one or more reflecting devices can beconfigured to re-direct and/or steer the LIDAR output signal so as toprovide scanning of the LIDAR output signal. Suitable reflecting devicesinclude, but are not limited to, mirrors such mechanically drivenmirrors and Micro Electro Mechanical System (MEMS) mirrors. The one ormore collimating devices provide collimation of the LIDAR output signaland can accordingly increase the portion of the LIDAR input signal thatis received in the utility waveguide 16. Suitable collimating devicesinclude, but are not limited to, individual lenses and compound lenses.

FIG. 3 illustrates the above chip used with a reflecting device 90 and acollimating device 92. For instance, a lens serves as a collimating orfocusing device that receives the LIDAR output signal and providescollimation or focusing of the LIDAR output signal. A mirror serves as areflecting device 90 that receives the LIDAR output signal and reflectsthe LIDAR output signal in the desired direction. As is illustrated bythe arrow labeled A, the electronics can move the mirror so as to steerthe collimated or focused LIDAR output signal and/or scan the collimatedor focused LIDAR output signal. The movement of the mirror can be in twodimensions or three dimensions. Suitable mirrors include, but are notlimited to, mechanically driven mirrors and Micro Electro MechanicalSystem (MEMS) mirrors.

FIG. 4 illustrates the above chip used with a reflecting device 90 and acollimating or focusing device 92. For instance, a mirror serves as areflecting device 90 that receives the LIDAR output signal and reflectsthe LIDAR output signal in the desired direction. As is illustrated bythe arrow labeled A, the electronics can move the mirror so as to steerthe LIDAR output signal and/or scan the LIDAR output signal. A lensserves as a collimating or focusing device 92 that receives the LIDARoutput signal from the mirror and provides collimation or focusing ofthe LIDAR output signal. The lens can be configured to move with themovement of the mirror so the lens continues to receive the LIDAR outputsignal at different positions of the mirror. Alternately, the movementof the mirror can be sufficiently limited that the lens continues toreceive the LIDAR output signal at different positions of the mirror.The movement of the mirror can be in two dimensions or three dimensions.Suitable mirrors include, but are not limited to, mechanically drivenmirrors and Micro Electro Mechanical System (MEMS) mirrors.

Technologies such as SOI MEMS (Silicon-On-Insulator Micro ElectroMechanical System) technology can be used to incorporate a reflectingdevice such as a MEMS mirror into the chip. For instance, FIG. 5 is across section of a portion of the chip taken through the longitudinalaxis of the utility waveguide 16. The illustrated chip was constructedon silicon-on-insulator waveguide. A mirror recess extends through thelight-transmitting medium to the base. The mirror is positioned in themirror recess such that the mirror receives the LIDAR output signal fromthe utility waveguide. A lens serves as a collimating or focusing device92 that receives the LIDAR output signal from the mirror and providescollimation or focusing of the LIDAR output signal. The lens can beconfigured to move with the movement of the mirror so the lens continuesto receive the LIDAR output signal at different positions of the mirror.Alternately, the movement of the mirror can be sufficiently limited thatthe lens continues to receive the LIDAR output signal at differentpositions of the mirror. The electronics can control movement of themirror in two or three dimensions.

The above chips can include alternative methods of scanning and/orsteering the LIDAR output signal in addition to a reflecting device oras an alternative device. For instance, the chip can include a componentfor splitting the outgoing LIDAR signal into multiple output signals.The chip can then tune the phase difference between different outputsignals so as to control the direction that the LIDAR output signaltravels away from the chip. The LIDAR output signal can be steered orscanned by changing the level of the phase difference between the outputsignals. Suitable systems that employ phase differential between outputsignals to steer a LIDAR output signal are described in U.S. PatentApplication Ser. No. 62/683,958, filed on Jun. 12, 2018, andincorporated herein in its entirety and in U.S. Patent Application Ser.No. 62/680,787, filed on Jun. 5, 2018, and incorporated herein in itsentirety.

Another alternative for scanning and/or steering the LIDAR output signalcan include optical switching. FIG. 6 illustrates a LIDAR system thatincludes a LIDAR chip and a redirection component. In FIG. 6, a portionof the LIDAR chip is illustrated. The illustrated portion of the LIDARchip is configured to use optical switching to steer a LIDAR outputsignal. The portion(s) of the chip that are not illustrated in FIG. 6can be constructed as described elsewhere in this Patent Application.For instance, the utility waveguide 16 shown in FIG. 6 can be theutility waveguide 16 of a LIDAR chip such as the LIDAR chip disclosed inthe context of FIG. 1.

The utility waveguide 16 carries the outgoing LIDAR signal to an opticalswitch 100 that directs the outgoing LIDAR signal to one of multiplealternate waveguide 102 that are each associated with a waveguide indexn=1 through N. Each of the alternate waveguides 102 terminates at afacet 18. The alternate waveguide 102 that receives the outgoing LIDARsignal guides the outgoing LIDAR signal to a facet 18 through which theoutgoing LIDAR signal exits from the alternate waveguide 102 and servesas the LIDAR output signal. Accordingly, the optical switch 100 candirect the outgoing LIDAR signal to any one of the facets 18 throughwhich the outgoing LIDAR signal passes and serves as a LIDAR outputsignal.

The LIDAR output signal can be reflected off an object located off ofthe chip. At least a portion of the reflected signal travels back to thefacet 18 through which it exited the alternate waveguide and enters theassociated alternate waveguide 102 as a LIDAR input signal. Thealternate waveguide 102 guides the LIDAR input signal to the opticalswitch 100 which directs the LIDAR input signal back to the utilitywaveguide 16. The chip and electronics can then process the LIDAR inputsignal.

The electronics can operate the optical switch 100 so as to change thealternate waveguide 102 that receives the outgoing LIDAR signal.Accordingly, the electronics can cause the outgoing LIDAR signal to bedirected to a particular one of the alternate waveguides 102 andaccordingly to a particular one of the facets 18.

The LIDAR system also includes a redirection component configured toreceive the outgoing LIDAR signal from any one of the alternatewaveguides and to redirect the received outgoing LIDAR signal such thata direction that the outgoing LIDAR signal travels away from theredirection component is a function of the alternate waveguide fromwhich the redirection component receives the outgoing LIDAR signal. Thedirection of the outgoing LIDAR signal can be a function of thealternate waveguide in that the direction that the outgoing LIDAR signaltravels away from the redirection component changes in responses tochanges in the alternate waveguide from which the redirection componentreceives the outgoing LIDAR signal. In some instances, the redirectioncomponent is configured such that none of the different directions isparallel to one another. For instance, the redirection component can beconfigured such that the outgoing LIDAR signal travels away from theredirection component at a different transmission angle when theredirection component receives the outgoing LIDAR signal from differentalternate waveguides where the transmission angle being measuredrelative to the redirection component.

In FIG. 6, a lens 104 serves as the redirection component 103. The lens104 that is positioned to receive the outgoing LIDAR signals that servesas the LIDAR output signal. The lens 104 and alternate waveguides 102are arranged such that LIDAR output signals from different alternatewaveguides 102 are incident on different regions of an input side of thelens 104 and/or have a different incident angle on the input side of thelens 104. As a result, LIDAR output signals from different alternatewaveguides 102 travel away from the lens 104 in different directions.For instance, the alternate waveguides 102 are labeled n=1 through n=Nin FIG. 6. The transmission angle of the LIDAR output signals (outgoingLIDAR signal) when the redirection component 103 receives the LIDARoutput signal from the alternate waveguide labeled n=1 through N islabeled θ_(n) in FIG. 6. Accordingly, when the LIDAR output signal isdirected to the alternate waveguide labeled n=1, the LIDAR output signalhas transmission angle θ_(n). The transmission angle is measuredrelative to the redirection component 103. For instance, thetransmission angle can be measured between the optical axis of the lensand the LIDAR output signal. As is evident from FIG. 6, the angle θ_(n)is different for different alternate waveguides 102. Since the LIDARoutput signals from different alternate waveguides 102 travel away fromthe lens 104 in different directions, the electronics can control thedirection of the LIDAR output signal by operating the switch so as todirect the outgoing LIDAR signal to the alternate waveguide 102 thatprovides the LIDAR output signal with the desired direction. The degreeof change in direction from one alternate waveguide 102 to anotheralternate waveguide 102 can be a function of the lens construction.Accordingly, the lens construction can be altered to increase ordecrease the degree of change in direction between alternate waveguides.

During operation of the system, the electronics can delay switching thealternate waveguide 102 that receives the outgoing LIDAR signal untilthe chip has received the LIDAR input signal that is needed for thedesired processing. As a result, the LIDAR output signal and theassociated LIDAR input signal are guided by the same alternate waveguide102.

In FIG. 6, R represents the radius of the LIDAR output signal at theinput side of the lens, R′ represents the lens radius, and s representsthe object distance from the lens. The value of R′ can be selected toincrease the amount of diverging light that is captured by the lens. Theratio of R/s can be used to approximate the value needed for R′ and canbe a function of the divergence angle of the light from the waveguidefacet. To increase capture of the diverging light, twice the divergencehalf angle ϕ, can be used. In that case, R/s can be at least equal totan(2ϕ). For example, for an alternative waveguide facet dimension of 10μm in the lateral direction, the lateral divergence half angle ϕ, isapproximately 6°. In that case R/s can be at least equal to)tan(12°=1/5.R′ represents the lens radius which can be larger than the half-width ofthe LIDAR output signal (R) to accommodate the change in position of theLIDAR output signal on the lens due to switching between the alternatewaveguides. In some instances, the R′ is greater than or equal to R,1.3R, or 1.6R and/or less than or equal to 4R, or 6R where R is greaterthan or equal to s*tan(2ϕ).

The center-to-center distance of the facets 18 is labeled d in FIG. 6.The angular resolution can be improved by decreasing d. In someinstances, the center-to-center distance is constant for each adjacentpair of facets. However, the center-to-center distance can be differentfor different pairs of facets. A suitable center-to-center distancebetween facets 18 includes, but is not limited to, distances greaterthan 5, 10, or 50 μm and/or less than 100, 1,000, or 10,000 μm.

The maximum value for N can be the nearest integer value to(1+2(R′−R)/d) where R is the diameter of the LIDAR output signals at theinput side of the lens 104 and R′ is the lens radius. Accordingly, thechip can include a number of alternate waveguides 102 less than or equalto the nearest integer value of (1+2(R′−R)/d). In some instances, N isgreater than or equal to 5, 10, or 50 and/or less than 100, 500, or1000. The angular range that can be scanned (2θ_(N)) by sequentiallydirecting the LIDAR output signal to each of the alternate waveguides102 can be increased by increasing N. Accordingly, an improvedresolution can be obtained by decreasing d and an improved scan rangeobtained by increasing N within the limits of the optical system.

The lens 104 can be configured such that the lens 104 collimates theLIDAR output signals from different facets. Additionally or alternately,the lens 104 can be positioned such that one or more of the facets islocated at a focal point of the lens 104. However, the focal points aretypically positioned along an arced line. For instance, FIG. 7illustrates the focal points for a lens having a focal length of 25 mm.The y-axis represents the distance of the center of a facet 18 from theoptical axis of the lens. The lens is positioned at x=0 mm. In order forthe facets to be positioned at the focal points of the lens, the facetswould be positioned along the arced line in FIG. 7. As illustrated inFIG. 8A, the chip can be constructed such that the facets 18 arepositioned along an arced line (the dashed line). A chip constructed ona silicon-on-insulator wafer can be provided with facets 18 positionedalong an arced line by etching the facets 18 in the siliconlight-transmitting medium. As is evident from FIG. 8A, this arrangementcan result in all or a portion of the facets 18 being positioned backfrom an edge of the chip or from an edge of the substrate. Alternately,the edge of the chip can be arced and the facets 18 can be positioned atan edge of the chip.

As an alternative to the positioning the facets 18 along an arced focalpoint line or in addition to positioning the facets along an arced focalpoint line, the alternate waveguides 102 can be curved such thatdirection of propagation of the outgoing LIDAR signals at the facets ofdifferent alternate waveguides 102 is different for different alternatewaveguides 102. For instance, FIG. 8B illustrates a portion of thealternate waveguides 102 curved so that the outgoing LIDAR signalsapproach the facets 18 from different directions. The curving of thealternate waveguides 102 can couple additional light into the lens.Although FIG. 8B illustrates the facets positioned along the arced focalpoint line, the facets need not be positioned along the arced focalpoint line.

Another alternative is to angle the chip and/or the facets such that thepositions of at least a portion of the facets 18 are positioned along aline that approximates the arced focal point line. In particular, thefacets 18 on one side of the optical axis of the lens can be positionedalong a line that approximates the arced focal point line. For instance,FIG. 9 illustrates a LIDAR chip having facets 18 positioned along a lineangled such that the facets for alternate waveguides n=f through n=N arepositioned along an approximation of the arced focal point line.However, the facets for alternate waveguides n=(f−1) through n=1 becomefurther away from the arced focal point line as they approach alternatewaveguides n=1. As a result, the electronics may not operate all or aportion of alternate waveguides n=(f−1) through n=1. Alternately, thechip can be constructed without all or a portion of alternate waveguidesn=1 through n=(f−1). Alternately, the chip can positioned such that all,more than 50%, or more than 75% of the facets are on the same side ofthe optical axis.

Positioning the chip such that the facets 18 are positioned along a linethat approximates the arced focal point line can include positioning thechip such that a portion of the facets 18 are positioned on one side ofthe arced focal point line and another portion of the facets arepositioned on another side of the arced focal point line. In someinstances, the chip includes the facets arranged such that a line canpass through each of the facets and the chip is positioned such that aportion of the facets 18 are positioned on one side of the arced focalpoint line and another portion of the facets 18 are positioned onanother side of the arced focal point line and the arced focal pointline passes through the line through the facets 18 at least two times.FIG. 10 provides an illustration of this arrangement where the dashedline represents the focal point line and a portion of the edge of thechip represents a line segment through the facets 18. Since the facetsare often non-perpendicular to the direction of propagation in theassociated alternate waveguide, the line through the facets is often notparallel to the plane of each of the facets.

Although the lens is illustrated as being spaced apart from the chip,the lens can be integrated with the chip. For instance, FIG. 11illustrates a portion of the above chip(s) modified to include a lens104. The lens is optically aligned with the facets 18 of the alternatewaveguides such that the lens 104 receives the LIDAR output signals. Thelens can be positioned in a recess 106. When the chip is constructed ona silicon-on-insulator the recess can extend into or through thelight-transmitting medium. In some instances, the recess extends throughthe light-transmitting medium and into the base. For instance, therecess can extend through the light-transmitting medium and into orthrough the buried layer. In some instances, the recess extends throughthe buried layer and into the substrate. In some instances, the lens isa separate component that is attached to the chip using technologiessuch as micro-optical assembly, and pick-and-place technology. In someinstances, the lens is an integral chip component formed usingtechnologies such as etching. For instance, when the chip is constructedon a silicon-on-insulator the lens can be formed by etching thelight-transmitting medium.

Suitable optical switches for use with the chip include, but are notlimited to, cascaded 2×2 Mach-Zehnder (MZ) modulators interferometersusing thermal or free-carrier injection phase shifters, and micro-ringresonator switches.

Although the above discussion uses a lens as a redirection component,other redirection components can be employed. For instance, a mirror canbe used in place of the lens. Suitable mirrors include, but are notlimited to curved mirrors such as parabolic curved mirrors. In someinstances, the mirror is angled to reflect the LIDAR output beams aboveor below the surface of the LIDAR chip and or facets polished at anangle may be used to direct the LIDAR output signals initially above theplane of the chip. FIG. 12A illustrates a LIDAR system that includesanother embodiment of a redirection component 103. In FIG. 12A, aportion of the LIDAR chip is illustrated. The illustrated portion of theLIDAR chip is configured to use optical switching to steer a LIDARoutput signal. The portion(s) of the chip that are not illustrated inFIG. 12A can be constructed as described elsewhere in this PatentApplication. For instance, the utility waveguide 16 shown in FIG. 12Acan be the utility waveguide 16 of a LIDAR chip such as the LIDAR chipdisclosed in the context of FIG. 1.

The utility waveguide 16 carries the outgoing LIDAR signal to an opticalswitch 100 that directs the outgoing LIDAR signal to one of multiplealternate waveguide 102. The alternate waveguide 102 that receives theoutgoing LIDAR signal guides the outgoing LIDAR signal to theredirection component 103. Although the redirection component of FIG. 6is located off the LIDAR chip, the redirection component of FIG. 12A canbe integrated into the LIDAR chip.

The electronics can operate the optical switch 100 so as to change thealternate waveguide 102 that receives the outgoing LIDAR signal.Accordingly, the electronics can cause the outgoing LIDAR signal to bedirected to a particular one of the alternate waveguides 102.

The redirection component is configured to receive the outgoing LIDARsignal from any one of the alternate waveguides and then direct thereceived outgoing LIDAR signal such that outgoing LIDAR signals receivedfrom different alternate waveguides travel away from the redirectioncomponent 103 in different directions. In some instances, theredirection component is configured such that none of the differentdirections is parallel to one another.

The redirection component 103 includes a splitter 110 that divides theoutgoing LIDAR signal into multiple output signals that are each carriedon a steering waveguide 112. Each of the steering waveguides 112 ends ata facet 18. The facets 18 are arranged such that the output signalsexiting the chip through the facets 18 combine to form the LIDAR outputsignal and/or to effectively re-form the outgoing LIDAR signal.

The splitter 110 and steering waveguides 112 can be constructed suchthat there is not a phase differential between output signals at thefacet 18 of adjacent steering waveguides 112. For instance, the splitter110 can be constructed such that each of the output signals is in-phaseupon exiting from the splitter 110 and the steering waveguides 112 caneach have the same length. Alternately, the splitter 110 and steeringwaveguides 112 can be constructed such that there is a linearlyincreasing phase differential between output signals at the facet 18 ofadjacent steering waveguides 112. For instance, the steering waveguides112 can be constructed such that the phase of steering waveguide numberj is f_(o)+(j−1)f where j is an integer from 1 to M and represents thenumber associated with a steering waveguide when the steering waveguidesare sequentially numbered as shown in FIG. 12A, f is the phasedifferential between neighboring steering waveguides when the phasetuners (discussed below) do not affect the phase differential, and f_(o)is the phase of the output signal at the facet 18 of steering waveguidej=1. In some instances, this phase differential is achieved byconstructing the steering waveguides such that the steering waveguideshave a linearly increasing length differential. For instance, the lengthof steering waveguide j can be represented by l_(o)+(j−1)Δl where j isan integer from 1 to M and represents the number associated with asteering waveguide when the steering waveguides are sequentiallynumbered as shown in FIG. 12A, Δl is the length differential betweenneighboring steering waveguide, and L_(o) is the length of steeringwaveguide j=1. When the steering waveguides are the same length, thevalue of Δl is zero and the value of f is zero. Suitable Δl include, butare not limited to, Δl greater than 0, or 5 and/or less than 10, or 15μm. Suitable f include, but are not limited to, f greater than 0π, or 7πand/or less than 15π, or 20π. Suitable M include, but are not limitedto, M greater than 10, 100, or 1000 and/or less than 10000, or 50000.

A phase tuner 104 can be positioned along at least a portion of thesteering waveguides 102. Although a phase tuner 104 is shown positionedalong the first and last steering waveguide, these phase tuners areoptional. For instance, the chip need not include a phase tuner onsteering waveguide j=1.

The electronics can be configured to operate the phase tuners so as tocreate a phase differential between the output signals at the facet 18of adjacent steering waveguides 102. The electronics can operate thephase tuners such that the phase differential is constant in that itincreases linearly across the steering waveguides. For instance,electronics can operate the phase tuners such that the tuner-inducedphase of steering waveguide number j is (j−1)α where j is an integerfrom 1 to M and represents the number associated with a steeringwaveguide 112 when the steering waveguides 112 are sequentially numberedas shown in FIG. 12, α is the tuner-induced phase differential betweenneighboring steering waveguides. Accordingly, the phase of steeringwaveguide number j is f_(o)+(j−1)f+(j−1)α. FIG. 12 illustrates the chiphaving only 4 steering waveguides in order to simplify the illustration,however, the chip can include more steering waveguides. For instance,the chip can include more than 4 steering waveguides, more than 100steering waveguides, or more than 1000 steering waveguides and/or lessthan 5000 steering waveguides.

The electronics can be configured to operate the phase tuners so as totune the value of the phase differential α. Tuning the value of thephase differential α changes the direction that the LIDAR output signaltravels away from the chip (θ). Accordingly, the electronics can scanthe LIDAR output signal by changing the phase differential α. The rangeof angles over which the LIDAR output signal can be scanned is ϕ_(R)and, in some instances, extends from ϕ_(v) to −ϕ_(v) with ϕ=0° beingmeasured in the direction of the LIDAR output signal when α=0. When thevalue of Δl is not zero, the length differential causes diffraction suchthat light of different wavelengths travels away from chip in differentdirections (θ). Accordingly, there may be some spreading of the outgoingLIDAR signal as it travels away from the chip. Further, changing thelevel of diffraction changes the angle at which the outgoing LIDARsignal travels away from the chip when α=0°. However, providing thesteering waveguides with a length differential (Δl≠0) can simplify thelayout of the steering waveguides on the chip.

The alternate waveguides 102 are constructed such that differentalternate waveguides 102 guide the outgoing LIDAR signal to differentlocations on an input side of the splitter 110. The splitter isconstructed such that the output signals enter the steering waveguides112 with a phase differential that changes in response to the locationwhere the outgoing LIDAR signal enters the splitter 110. As a result,the phase differential between the output signals changes based on whichalternate waveguide the outgoing LIDAR signal uses to enter the splitter110. The splitter 100 can be wavelength independent in contrast to ademultiplexer. Examples of wavelength independent splitters where thephase differential between the output signals changes in response to thelocation where the outgoing LIDAR signal enters the splitter 110include, but are not limited to, star couplers.

Since the phase differential between the output signals changes based onthe alternate waveguide the outgoing LIDAR signal uses to enter thesplitter 110, the direction that resulting LIDAR output signal travelsaway from the redirection component is a function of the alternatewaveguide 102 that the outgoing LIDAR signal uses to enter the splitter110. As a result, the LIDAR output signal can be associated withdifferent alternate waveguides 102. For instance, FIG. 12A illustrates aLIDAR output signals that includes several different modes labeled LOSEwhere the n corresponds to the alternate waveguide 102 indices n=1through N. As a result, the light for LOS₂ (LIDAR output signal mode 2)enters the splitter 110 on the alternate waveguide 102 with index n=2and the light for LOS_(N) enters the splitter 110 on the alternatewaveguide 102 with index n=N. Since each of the LOS₁ through LOS_(N)travels away from the redirection component 103 in different directions,the direction that the LIDAR output signal (the outgoing LIDAR signal)travels away from the redirection component 103 changes in response tochanges in the alternate waveguide 102 on which the outgoing LIDARsignal entered the splitter 110. Because this change in direction occursdue to a phase shift induced by the splitter 110, the phase shifters 114need not be operated or changed to cause the change in direction shownin FIG. 12A. As a result, the electronics can change the direction ofthe LIDAR output signal (the outgoing LIDAR signal) by changing thealternate waveguide 102 to which the optical switch 100 directs theoutgoing LIDAR signal.

Because the optical switch 100 can also be used to affect the phasedifferential between adjacent output signals at the facet 18 of adjacentsteering waveguides, the phase differential between adjacent outputsignals at the facet 18 of adjacent steering waveguides can be afunction of one or more factors selected from the group consisting ofconstruction of the splitter 110, construction of the steeringwaveguides 112, the operation of any phase tuners 104, and the alternatewaveguide 102 to which the outgoing LIDAR signals is directed. As aresult, the direction that the LIDAR output signal travels away from theredirection component 103 is a function of one or more factors selectedfrom the group consisting of construction of the splitter 110,construction of the steering waveguides 112, the operation of any phasetuners 104, and the alternate waveguide 102 to which the outgoing LIDARsignals is directed.

More than one of these factors can be used to tune the direction of theoutgoing LIDAR signal. For instance, the optical switch 100 and thephase tuners 104 can be used together to tune the direction of the LIDARoutput signal. Each of the LIDAR output signals labeled LOS_(n) in FIG.12A can be tuned over an angular range ϕ_(n) using the phase tuners 104.The angular range over which the LIDAR output signal labeled LOS₂ inFIG. 12A can be tuned using the phase tuners 104 is labeled ϕ₂ in FIG.12B and the angular range over which the LIDAR output signal labeledLOSS in FIG. 12A can be tuned using the phase tuners 104 is labeled ϕ₃in FIG. 12B. Each of the angular ranges covers angles from ϕ_(n,a) toϕ_(n,b) where the angles covered by each of the different angular rangescan be different such that no two angular ranges have the same to valuesfor ϕ_(n,a) and ϕ_(n,b). As is shown in FIG. 12B, in some instances, theredirection component is configured such that the angular ranges fordifferent LIDAR output signal modes (LOS_(n)) overlap one another. As aresult, by combining the steering provided by the phase tuners (ϕ_(n))with the steering provided by the optical switch, the LIDAR outputsignal can be steered within a continuous range of directions over thefull field of view.

A variety of approaches can be used to increase the angular ranges forthe LIDAR output signal modes (LOS_(n)). For instance, increasing theseparation between the waveguides 102 can increase the angular rangesfor the LIDAR output signal modes (LOS_(n)).

When the selection of the alternate waveguide 102, the construction ofthe splitter 110 and steering waveguides 112 and the operation of anyphase tuners 104 is such that the phase differential between adjacentoutput signals at the facet 18 of adjacent steering waveguides 112changes linearly, the resulting LIDAR output signals are collimated.When the selection of the alternate waveguide 102, the construction ofthe splitter 110 and steering waveguides 112 and the operation of anyphase tuners 104 is such that the phase differential between adjacentoutput signals at the facet 18 of adjacent steering waveguides 112changes non-linearly, the resulting LIDAR output signals can be focused.Accordingly, the level of divergence, collimation, or focus can beselected by construction of one or more factors selected from the groupconsisting of the selection of the alternate waveguide 102, theconstruction of the splitter 110, construction of the steeringwaveguides 112 and the operation of any phase tuners 104.

The LIDAR output signal can be reflected off an object located off ofthe chip. At least a portion of the reflected signal travels from theback into the steering waveguides 112 and enters the alternate waveguide102 from which the outgoing LIDAR signal originated as a LIDAR inputsignal or incoming LIDAR signal. The alternate waveguide 102 guides theLIDAR input signal to the optical switch 100 which directs the LIDARinput signal back to the utility waveguide 16. The chip and electronicscan then process the LIDAR input signal as described elsewhere in thisapplication.

During operation of the system, the electronics can delay switching thealternate waveguide 102 that receives the outgoing LIDAR signal untilthe chip has received the reflected LIDAR input signal that is neededfor the desired processing. As a result, the LIDAR output signal and theassociated LIDAR input signal are guided by the same alternate waveguide102.

The optical switch 100 may be monolithically integrated on the sameLIDAR chip, or may be separate from the LIDAR chip and connected by anoptical fiber.

Other embodiments, combinations and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

1. An optical system, comprising: a LIDAR chip that includes a switchconfigured to direct an outgoing LIDAR signal to one of multipledifferent alternate waveguides; a redirection component configured toreceive the outgoing LIDAR signal from any one of the alternatewaveguides and configured to redirect the received outgoing LIDAR signalsuch that a direction that the outgoing LIDAR signal travels away fromthe redirection component changes in response to changes in thealternate waveguide from which the redirection component receives theoutgoing LIDAR signal, the redirection component including a splitterconfigured to receive the outgoing LIDAR signal from any one of thealternate waveguides and to split the outgoing LIDAR signal intomultiple output signals; and multiple steering waveguides that are eachconfigured to receive a different one of the output signals.
 2. Thesystem of claim 1, wherein the redirection component is configured suchthat the outgoing LIDAR signal travels away from the redirectioncomponent in a different direction when the redirection componentreceives the outgoing LIDAR signal from different alternate waveguides.3. The system of claim 1, wherein the redirection component isconfigured such that the outgoing LIDAR signal travels away from theredirection component at a different transmission angle when theredirection component receives the outgoing LIDAR signal from differentalternate waveguides, the transmission angle being measured relative tothe redirection component.
 4. The system of claim 1, wherein none of thedirections that the outgoing LIDAR signal travel away from theredirection component are parallel to one another.
 5. The system ofclaim 1, wherein the splitter is a wavelength independent splitter. 6.The system of claim 5, wherein the steering waveguides each terminatesat a facet and the facets are arranged such that output signals exitingfrom the steering waveguides through the facets combine to re-form theoutgoing LIDAR signal with the re-formed outgoing LIDAR signal travelingaway from the redirection component.
 7. The system of claim 6, whereinthe steering waveguides each includes a phase tuner configured to tune aphase differential between output signals in the steering waveguides soas to tune a direction that the reformed outgoing LIDAR signal travelsaway from the redirection component.
 8. The system of claim 7, furthercomprising: electronics configured to operate the phase tuners such thatthe outgoing LIDAR signal is collimated as it travels away from theredirection component.
 9. The system of claim 7, wherein the phasetuners are configured to tune the direction that the reformed outgoingLIDAR signal travels away from the redirection component over multipleangular ranges where each of the different angular ranges is associatedwith a different one of the alternate waveguides.
 10. The system ofclaim 9, wherein each of the angular ranges covers different angles andthe angular ranges associated with adjacent alternate waveguidesoverlap.
 11. The system of claim 1, wherein there is not a phasedifferential between output signals at facet of adjacent steeringwaveguides.
 12. The system of claim 1, wherein there is a linearlyincreasing phase differential between output signals at facet ofadjacent steering waveguides.